PROJECT SUMMARY Sarcoidosis is an adult onset systemic inflammatory disease that can compromise the function of vital organs. The lungs are most commonly affected, a manifestation that is readily detected with conventional diagnostic tests (e.g., chest radiography). However, sarcoidosis of the heart [cardiac sarcoidosis (CS)] and central nervous system [neurosarcoidosis (NS)] is present in a significant subset of sarcoidosis patients and these manifestations are more difficult to detect. It is important to identify CS and NS because involvement of these organs contributes significantly to the overall morbidity and mortality of sarcoidosis. Preliminary studies in our laboratory indicate that circulating subcellular components, referred to as exosomes, contain small RNA (microRNA) that can serve as biomarkers of sarcoidosis, and may be able to identify which organs are affected. We posit that exosome-derived microRNA will allow us to specifically detect CS and NS. In Aim 1 we propose to use plasma samples obtained from sarcoidosis patients with well-documented cardiac involvement to determine if circulating endosome-derived microRNA reliably detects CS, and we will further determine the specificity of circulating exosome-derived microRNA in CS patients relative to patients with ischemic heart disease. Aim 2 of the proposal will establish if circulating exosome-derived microRNA can be used as biomarkers of NS, and will further determine if these biomarkers can distinguish NS from CS. These studies will be performed using banked samples provided by the NIH BioLINCC repository, and banked samples available from the recently completed NIH sponsored Genomic Research of Alpha-1 Antitrypsin Deficiency and Sarcoidosis (GRADS) trial. For each research Aim exosome-derived microRNA expression will be assessed quantitatively in a smaller test cohort using next-generation sequencing and the most promising microRNA biomarkers will be validated in a second cohort using quantitative real-time polymerase chain reaction (qRT-PCR). These studies will guide the design of subsequent prospective trials that would establish circulating exosome-derived microRNA as organ-specific sarcoidosis biomarkers.